Unit 2: Branch Circuits Flashcards
Identify branch circuit components, differentiate circuit types, and calculate proper sizing and overcurrent protection.
Fill in the blank:
Where conduits enter a floor-standing switchboard, switchgear or, panelboard at the bottom, the conduits, including their end fittings, shall not rise more than ________ above the bottom of the enclosure.
3 in.
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For emergency systems where internal combustion engines are used as the prime mover, an on-site fuel supply shall be provided with an on-site fuel supply sufficient for not less than ________ full-demand operation of the system.
2 hours
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Conductors supplying outlets for arc and xenon motion picture projectors of the professional type shall be a MINIMUM size of ________ and shall have an ampacity of not less than the projector current rating.
8 AWG
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Thermostatically controlled switching devices serving as both controllers and disconnecting means for fixed electric space heating equipment shall be designed so that the circuit cannot be energized automatically after the device has been manually placed in the ________.
OFF position
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A bonding jumper connected between the communications grounding electrode and power grounding electrode system at the building or structure service where separate electrodes are used shall not be smaller than size ________ copper.
6 AWG
Given: A straight pull of size 4 AWG and larger conductors is to made in a junction box that will have a trade size 3 in. conduit and two (2) trade size 2 in. conduits entering on the same side and exiting on the opposite wall. No splices or terminations will be made in the box. Which junction box is the MINIMUM required for this installation?
24 in. x 24 in.
Given: A dairy farm supplied with a 120/240-volt, single phase electrical system will have the following three loads supplied from a common service; one – 18,000 VA, one - 16,000 VA, and one – 10,000 VA. What is the demand load, in amperes, on the ungrounded service-entrance conductors?
152 amperes
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All 15- or 20-ampere, single-phase, 125-volt receptacles located within at LEAST ________ of the edge of a decorative fountain shall be provided with GFCI protection for personnel.
20 feet
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The emergency electrical disconnects for attended self service gasoline stations or convenience stores with motor fuel dispensing facilities must be located not more than ________ from the motor fuel dispensers that they serve.
100 feet
Given: A dry-type transformer is fed with four (4) parallel size 500 kcmil conductors per phase. The conductors enter the enclosure on the opposite wall of the terminals. What is the MINIMUM wire-bending space required for the conductors?
16 in.
What MINIMUM size THWN copper conductors are required to supply a continuous-duty, 25 hp, 208-volt, 3-phase motor, where the motor is on the end of a short conduit run that contains only three (3) conductors, at an ambient temperature of 115 deg. F?
1 AWG
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Where time-delay (dual-element) fuses are used for short-circuit and ground-fault protection for both windings of a part-winding synchronous motor, the fuses shall be permitted to have a rating not exceeding ________ of the full-load current of the motor.
150%
Where a conductor is marked RHW-2 on the insulation, what does the -2 represent?
The conductor has a maximum operating temperature of 90ºC.
Apply the general method of calculation for dwellings and determine the demand load, in kW, on the ungrounded service-entrance conductors for four (4) household electric ranges rated 19 kW each.
23 kW
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As a general rule regarding movie theaters, all switches for controlling the emergency lighting systems shall be permitted to be located ________.
in the lobby
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Single-conductor cable Type ________ shall be permitted in exposed outdoor locations in photovoltaic source circuits for photovoltaic module interconnections within the photovoltaic array
USE-2
What percent of electrical supplied spaces in a recreational vehicle park must be equipped with at least one (1) 30-ampere 125-volt receptacle outlet?
70%
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Each operating room of a healthcare facility shall be provided with a MINIMUM of ________ listed “hospital grade” receptacles.
36
Where a 3-phase, 25 kVA rated transformer with a 480- volt primary and a 208Y/120-volt secondary is to be installed where both primary and secondary protection is required to be provided, determine the MAXIMUM standard ampere rating of the secondary overcurrent protection as permitted by the NEC®.
90 amperes
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Where ungrounded conductors are run in parallel in multiple raceways, the wire-type equipment grounding conductor, where used, shall be ________.
run in parallel in each raceway
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Where track lighting is installed in a continuous row, each individual section of not more than ________ in length shall be securely supported.
4 feet
Determine the MINIMUM size THWN copper feeder conductors required by the NEC® to supply the following 480 volt, continuous duty, 3-phase, induction-type, Design C, motors.
- one - 40 hp
- one - 50 hp
- one - 60 hp
4/0 AWG
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In health care facilities, essential electrical systems shall have a MINIMUM of ________ independent sources of power.
two (2)
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Where compressed natural gas vehicles are repaired in a commercial major repair garage, the area within ________ of the ceiling shall be considered unclassified where adequate ventilation is provided.
18 in.
